1. Field of the Invention
The invention is directed to a lightweight concave for a rotary agricultural combine having a bar and wire removable grid that is formed by projection welding.
2. Description of the Prior Art
Agricultural combines are large machines that harvest, thresh, separate and clean an agricultural crop. The resulting clean grain is stored in a grain tank located on the combine. The clean grain can then be transported from the grain tank to a truck, grain cart or other receiving bin by an unloading auger.
There are two basic types of combines: (1) a conventional combine having a transverse threshing cylinder and straw walkers, and (2) a rotary combine having a rotor and rotor casing for threshing and separating the harvested crop. The transverse threshing cylinder is mounted in close proximity to a concave. The rotating threshing cylinder in conjunction with the fixed concave threshes the crop material. The concave generally comprises a series of transversely extending bars through which are inserted axially running wires. A concave of this type forms a grate through which the majority of the threshed grain and chaff fall onto a collecting assembly where it is directed to the cleaning system of the combine. U.S. Pat. No. 4,909,772 illustrates such a concave. U.S. Pat. No. 5,024,631 discloses a conventional transverse threshing concave having a frame on which are mounted three removable sieve lining sections.
Rotary combines are provided with an infeed section for pulling crop material into the rotary crop processing assembly from the feederhouse, a threshing section for threshing the crop material, and a separating section for separating the grain from the threshed crop material. The rotary crop processing unit comprises a rotor that is surrounded by a casing. The bottom of the casing is provided with a series of grates through which the grain and chaff fall from the casing. The grates located beneath the threshing section of the rotary crop processing unit comprises a concave, such a concave is disclosed in U.S. Pat. No. 4,499,908. In this patent one side of the concave is pivotally mounted to the crop processing unit and the other side is adjustably mounted to the crop processing unit to control the clearance between the concave and rotor. U.S. Pat. Nos. 4,192,322 and 4,422,463 each show a spiral wire concave in which a spiral wire is welded to a series of axially extending spacer bars.
Projection welding is a form a resistance welding wherein the heat for the welding is derived from the localization of electrical resistance at predetermined points by means of projections. The projections maybe made of stamping or machining.